Responsive gastric stimulator

ABSTRACT

A responsive gastrointestinal stimulation device is provided where one or more sensors sense data corresponding to a subject or the gastrointestinal tract of a subject and responds to sensing the data by stimulating, adjusting stimulation, or stopping stimulation of the gastrointestinal tract. A stimulation device is also provided to stimulate the gastrointestinal tract to produce a sensation of satiety or to control hunger or food consumption.

This application is a Continuation-in-Part application of U.S. Ser. No.10/290,788 which is a Divisional of U.S. Ser. No. 09/847,884.

FIELD OF THE INVENTION

This invention relates to an implantable device, system and method forcontrolling electrical stimulation to the stomach wall in response tosensing information.

BACKGROUND OF THE INVENTION

Various organs of the gastrointestinal tract such as the stomach, smallintestine and colon contain cells that are believed to govern theorgans' periodic contractile behavior. In healthy humans, in certainregions of the organs, these cells generate and propagate rhythmicelectrical signals. In general, several types of electrical potentialactivity have been observed in the gastrointestinal tract. Consistentcyclic slow wave or pacesetter potentials have been observed and higherfrequency spike activity has been observed that may correspond to someextent with smooth muscle contractile activity and peristalsis. Thestomach and digestive system is also controlled by the nervous systemthat includes a highly complex enteric nervous system and to someextent, the central nervous system. It is believed that when thepacesetter potentials are combined with a chemical or neural excitationof the cells that smooth muscle contractile activity occurs. It is alsobelieved that stimulation of the stomach may effect a subject'ssensation of satiety through a complex system involving smooth musclestimulation or contractions, and neural and chemical pathways.

Obesity has become one of the leading causes of death in the UnitedStates. Electrical stimulation has been proposed to treat obesity bycausing a feeling of satiety, for example, by altering gastric motility.Some electrical stimulation is believed to interfere with the electricalpotential activity of the stomach and to slow the movement of foodthrough the stomach. Electrical stimulation may cause the stomach toretain food for a greater duration. This gastric retention among otherfactors may induce a sensation of satiety.

Electrical stimulation of the gastrointestinal tract has also beenproposed to treat motility related disorders and other gastrointestinaldiseases. The electrical stimulation has been proposed in a number offorms or for a number of applications, such as, e.g., pacing, electricalcontractile stimulation or other stimulation.

In some disease states, dysrhythmias of the gastric pacesetterpotentials may be present. Electrical pacing of gastric pacesetterpotentials has been proposed to induce regular rhythms for thepacesetter potentials with the intent of inducing regular or controlledgastric contractions. The result of abnormal pacesetter potentials maybe gastric retention of food. Electrical stimulation of gastric tissuehas also been proposed to induce peristalsis. Electrical stimulation hasalso been proposed to slow the gastric emptying to treat a disorderknown as dumping syndrome where the stomach empties at an abnormallyhigh rate into the small intestine causing various gastrointestinaldisorders.

An early attempt at a gastric stimulation device included an electrodeat the end of a nasogastric tube or catheter. The nasogastric tube waspassed into the stomach transnasally. Electrical stimulation was appliedusing an external stimulator unit through the electrode on the end ofthe tube. The return electrode was placed on the abdomen. This devicerequired a transnasal procedure whenever stimulation was required.

Other devices used to pace the stomach have generally been implanted byaccessing the outside of the stomach through an opening in the abdomen,either through open surgery or laparoscopic surgery. Electrodes havebeen attached to the stomach laparoscopically with attached leadsextending through the abdomen to a subcutaneously or sub-muscularlyimplanted electronics unit. The devices may be anchored into thesubcutaneous or sub-muscular pocket initially by a suture anchor and/oreventually by fibrous tissue ingrowth around the unit.

Other devices are described, for example in related U.S. Pat. No.6,535,764, fully incorporated herein by reference. U.S. Pat. No.6,535,764 describes a gastric stimulator that is implanted by deliveringthe device through the esophagus of a subject and attaching to thestomach wall from the inside of the stomach. Also, related U.S. patentapplication Ser. No. 10/109,296, fully incorporated herein by reference,describes a gastric stimulator that is implanted submucosally within thestomach wall.

Some gastric stimulation procedures have proposed electrical stimulationin response to sensing innate electrical pulses within the stomach thatfall within particular ranges. According to these procedures, sensingelectrical signals are indicators of when or how to stimulate or when orhow to stop stimulation. Additionally, a device has been proposed tosense electrical parameters to determine the fullness of an organ andthe absence of muscular contraction, and to deliver electrical muscularcontraction stimulation to the organ in response (i.e., presumably totreat gastro-paresis). However, some sensed electrical signals are notreliably detected and have not always corresponded with appropriateindicators of need for stimulation.

A gastrointestinal stimulator has be described that senses food beingswallowed by sensing motion (with an accelerometer), temperature, orpressure and responsively stimulates to coordinate contractions invarious gastrointestinal organs to prevent esophageal acid reflux or, toincrease speed of movement of food through the gastrointestinal tract(under the theory that less food will be absorbed when food moves morequickly through the stomach). As described, the stimulator stimulateswhen the gastrointestinal tract fails to act normally. While there hasbeen some success in gastric stimulation, it is believed that over timethe stomach may become desensitized to ongoing stimulation. Therefore,it would be desirable to provide a gastric stimulator that reducesdesensitization of the stomach from ongoing stimulation.

Also, implanted stimulators have limited battery life, particularly whenthe device is smaller. Accordingly, it would be desirable to provide adevice that operates to conserve battery life.

It would be desirable to provide a gastric stimulator that stimulatesthe stomach under predetermined circumstances or conditions or atappropriate times.

It would further be desirable to provide such a stimulator thatstimulates in order to produce a sensation of satiety.

Furthermore, to control eating disorders or to treat obesity, it wouldbe desirable to provide a stimulator that senses when food has beeningested and/or can regulate stomach contractions based onidentification of the contents of the stomach or according to an eatingregimen.

SUMMARY OF THE INVENTION

The present invention provides a device, system and method for treatingand/or diagnosing gastric disorders by applying an electrical signal oran electromagnetic field to tissue of the stomach for a therapeuticand/or diagnostic purpose. The invention also provides a device, systemand method for treating and/or diagnosing gastric disorders upon sensingone or more parameters, whereupon the device, system or methodstimulates the stomach, i.e., on-demand. The diagnostic or therapeuticpurpose may include, but is not limited to, controlling appetite,satiety, eating habits and/or obesity, treating nausea, facilitating orexpediting mixing or breaking down of food matter or liquids in thestomach, controlling, facilitating or expediting movement of food matteror liquids through the stomach and into the small intestine; andstimulating the stomach to delay passage of food from the stomach andinto the small intestine. The stimulation may affect the smooth musclecontractions, nerves associated with the stomach and/or biochemistry orsecretions at the stomach.

The invention also provides a device and method for optimizing oradjusting stimulation parameters in response to feedback from sensors.

In accordance with the invention, the device is controlled underpredetermined circumstances, conditions, or at predetermined times, bymodifying or turning on/off stimulation. Accordingly, the devicecomprises one or more sensors for sensing a particular parameter, andone or more responsive elements that determines a particular conditionor circumstance based on sensing at least one parameter, and thatresponds to sensing and/or determining a condition or circumstance. Onesuch response may be to cause the device to modify or turn on/offstimulation.

The sensors and responsive elements may include but are not limited to anumber of types of sensors and responsive elements and any combinationthereof. Sensing may be used over time to identify patterns diagnosediseases and evaluate effectiveness of various treatment protocols.According to the invention, sensors may be included in the device orseparately. The stimulation device may be programmed to deliverstimulation in response to sensed parameters. The sensors may sense aplurality of parameters in order to determine whether or not tostimulate or otherwise respond.

For example, a temperature sensor may sense a change in temperature or arate of change in temperature that indicates ingestion of food orliquid. A pH sensor may be used to determine when food has been ingestedor to determine when a subject is hungry and has increased acidsecretion. When the temperature or pH changes in a manner indicatingfood ingestion, the stimulation device may be instructed to deliverstimulation pulses to control gastric motility, i.e., to retain food. Anoptical emitter and sensor may be used to determine the presence and/orcomposition of such food. Pressure sensors may be used to sense motilitypatterns, e.g. presence, strength or frequency of contractions. Meanpressure shifts may be observed to identify gastric contractility. Amechanical sensor may sense, for example, stomach wall contractions.

Contractile sensor may include, for example, a piezo-electric,piezo-resistive, or strain gauge sensor positioned to mechanically sensecontractions. Alternatively, a polymeric variable resistive device maybe used to sense contractions. A screen-printed resistor may be suitableto sense local contraction, e.g., a change in resistive value may occurwhen the resistor bends contracts or stretches. A variable capacitorconstructed of flexible plates may also be used to sense contractions bydetecting when and the degree to which the distance between the plateschanges due to contractions.

According to one variation, stomach wall contractions are locally sensedwith a contraction sensor. The sensor senses contractions in proximityto a local stimulation site, e.g. adjacent or in proximity to astimulating electrode.

As the stomach contracts, the stomach wall typically becomes thicker. Inone embodiment a device is implanted in the stomach wall includes astrain gauge able to sense change in stomach wall thickness. As thestomach contracts, the impedance of the stomach wall changes. In oneembodiment, the sensor includes electrodes configured to sense impedanceof the stomach wall.

Biochemical sensors may be used to determine presence orquantity/concentration of a particular biochemical substance, forexample, stomach acid, enzyme or hormone secretions. The responsiveelement may responsively stimulate the stomach to control presence orquantities of such secretions. For example, acid secretions may becorrelated with hunger. The stomach may be stimulated to reduce hungerand to reduce acid secretions, which may include, e.g., acid, enzymes,or gastric satiety hormones such as Ghrelin.

The stimulation device may also use sensed parameters to program orreprogram the device stimulation program or protocol. For example,measuring impedance changes through a circuit coupled to the electrodes(e.g., delivering a constant current or voltage across the electrodes todetermine impedance) or determining the contractile behavior of thestomach using a contraction sensor, in response to stimulation pulses,the effectiveness of the stimulation pulses may be monitored andadjusted or ramped up to provide optimal response. The stimulationprogram may also include an automatic adjustment in response to changesin pressure measurement.

The responsive devices may comprise one or more sensors and one or moreresponsive elements that respond to information sensed by the sensors.The responsive element may process the sensor signal and may make adetermination of existence of a condition or circumstance andcorrespondingly respond.

Where a plurality of stimulation electrodes or stimulation sites ispresent, a plurality of sensors, each adjacent a particular site may beused to sense effectiveness of stimulation at the site. Stimulationparameters at each site or selection of stimulators may be made inresponse to sensed data.

Stomach contractions are sometimes associated with hunger. Theresponsive element may respond to contraction sensors that sense stomachcontractions, by stimulating to interfere with the stomach contractionsor to otherwise cause a sensation of satiety. The stimulation may bedirected to slow, stop or reverse the innate peristaltic contractionsthat tend to move food through the stomach. The responsive element mayrespond to information sensed by a contraction sensor by adjusting thestimulation. The responsive element may respond to the contractionsensor that senses local contractions adjacent a stimulation electrodeby adjusting the stimulation to elicit a different contraction response.Pulse amplitude, pulse width, frequency, burst repetition rate or otherparameters may be adjusted.

A responsive element may stimulate the stomach in response to atemperature sensor sensing the temperature within the stomach. Theresponsive element may determine when the temperature changes to apredetermined degree, at a predetermined rate, for a predetermined time,or a combination of the foregoing, such that it can be determined thatfood, or other material has been ingested. The stimulation may bedirected to cause gastric retention of food for a greater duration,e.g., by interfering with peristaltic contractions and/or the innateelectrical potentials of the stomach.

A responsive element may determine from a pH sensors sensing the pHwithin a stomach, when the pH has changed to a degree, at a rate, and/orover a period of time such that it indicates food or other material hasbeen ingested. Upon such a determination, the responsive element maystimulate to cause gastric retention of food. The pH sensor may alsoindicate hunger from an increase in gastric secretions. The responsiveelement may respond by stimulating to produce satiety, to prevent orreduce hunger, or to reduce secretions of the stomach.

A responsive element may respond to the detection of the presence,absence or detected quantity/concentration of a particular biochemicalcomposition, for example, by stimulating the stomach in response to acidor other secretions, to create a sensation of satiety, or to control thesecretions.

A responsive element may determine from sensed impedance of materials inthe stomach, when certain types of food have been ingested. Based on theimpedance characteristics of the contents of the stomach, the responsiveelement may determine when and how to stimulate.

A motion sensor or accelerometer may be used to sense movement relatingto respiration or gross subject movement, and, based on suchinformation, a responsive element may determine when a subject issleeping and turn off stimulation. Alternatively, the responsive devicemay determine when a subject's activity level is at an optimal level forstimulation, and only stimulate at such time. For example, theresponsive element may determine when an activity level is eithersleeping or relatively higher level of exertion, based on decreased orincreased respiration and/or gross movement characteristic of suchactivity levels. The responsive element may turn off or prevent turningon stimulation in response to sensing certain parameters and determiningthe existence of such conditions.

The responsive element may determine from a contraction sensor that thestomach is contracting to a given degree or at a given rate and inresponse, stimulate the stomach to interfere with contractions, or,where contractions may correlate to hunger, stimulate to cause asensation of satiety.

An optical sensor along with a light source may be located within thestomach. The light source is configured to emit light, and an opticalsensor is configured to either sense reflected light or to sense lighttransmitted through material located in the stomach. The sensor may beconfigured to sense light at predetermined wavelengths or the lightsource may emit light at predetermined wavelengths. The contents of thestomach may be qualitatively assessed based on the amount of light atone or more wavelengths that is transmitted or reflected. Thecomposition of the food may be determined based on the light reflectingor transmission characteristics of such food. Various characteristics offood or other material may be determined by emitting light at variousfood samples and determining characteristic light transmission orreflectance properties. This properties have been determined using foodspectroscopy techniques.

The stimulating (or diagnostic) device of the present inventiontypically includes stimulating electrodes attached or electricallycoupled to the stomach. The device may include, for example, electricalcircuitry residing within the patient's stomach or leads attached to thestomach and extending through the patient's body to a subcutaneouselectronics unit.

In one variation, the device includes: at least one stimulatingelectrode in electrical contact with the stomach wall; an electronicsunit containing the electronic circuitry of the device; and anattachment mechanism for attaching the device to the stomach wall. Oneor more stimulating electrodes may be secured to the wall of the stomachby an attachment device. One or more stimulating electrodes may also belocated on the electronics unit. The device may include electrodes or ahousing with electrodes implanted within the stomach wall, e.g.,subcutaneously. Another variation of a stimulator device may include astimulation device secured to the stomach with flexible leads attachedto the preferred stimulation site. Examples of such devices aredescribed in U.S. Pat. No. 6,535,764, and U.S. patent application Ser.Nos. 10/109,296 and 10/116,481 incorporated herein by reference.

The stimulation is provided through at least one pair of bipolar typeelectrodes. Alternatively, a relatively remote return electrode may beprovided in a monopolar type device.

Sensors for sensing various parameters of the stomach or correspondingto a particular condition or circumstance can be included with theelectrode assembly or separately. The sensors may be, for example:mounted on an electronics unit attached to a stomach wall, on anattachment mechanism that attaches an electronics unit or an electrodeto the stomach wall, on an attachment mechanism that separately attachesor otherwise positions the sensor at the stomach, or by other means, forexample, in an independently attached device attached or coupled to thepatient within the abdomen or at another location.

The contraction sensors may be used locally with respect to thestimulating electrodes. The contraction sensors may be used to determineideal or preferred stimulation parameters. The contraction sensors maybe used when a device is first implanted to program the stimulator todetermine the best response or a preferred response. This may be done byslowly ramping up stimulation until a desired response is elicited. Theparameters may be adjusted after the device has been used, to readjustthe parameters. The stimulation may be automatically, periodically orcontinuously readjusted in response to the contraction sensing.Accordingly, a substantially instantaneous response is detectable, i.e.an immediate local response to stimulation may be detected in proximityto the stimulation site.

Sensing may also be used over time to identify patterns, diagnosediseases and evaluate effectiveness of various treatment protocols.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of a system of an embodiment of the presentinvention including an electric stimulator as it is implanted in apatient's stomach.

FIG. 1B is an enlarged view of a portion of the system of FIG. 1A.

FIG. 2 is a schematic view, illustrating an embodiment of a stimulatoraccording to the invention implanted in a patient.

FIG. 3 is a schematic diagram of the circuit of an electronic stimulatorof the present invention.

FIG. 4 is a schematic diagram of the circuit of an externalprogrammer/recorder of the present invention.

FIG. 5 is an exemplary signal sensed by a temperature sensor over aperiod of time.

FIG. 6A is an exemplary signal sensed by an accelerometer over a periodof time.

FIG. 6B is an exemplary signal sensed by an accelerometer over a periodof time.

FIG. 7 is a stimulator with an optical sensor according to theinvention.

FIG. 8 is an enlarged perspective view of an alternative distal portionthe optical sensor shown in FIG. 7.

FIG. 9 is an enlarged perspective view of an alternative distal portionthe optical sensor shown in FIG. 7.

FIG. 10 is a flow diagram of a stimulation threshold determining deviceand method.

FIGS. 11A and 11B illustrate a device for optimizing electricalstimulation in the stomach.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1A and 1B, a stimulator 10 in accordance with theinvention is illustrated as it is implanted in a stomach 100. Thestimulator 10 is implanted through a patient's mouth 101, pharynx 102,esophagus 103, and then into the stomach 100 using endoscopic instrument110. A surgical placement method and stimulator are described in U.S.Pat. No. 6,535,764 incorporated herein by reference. Alternativestimulator attachment mechanisms and surgical implanting techniques arecontemplated, including but not limited to the stimulators andimplanting techniques described with reference to U.S. application Ser.Nos. 10/109,296 and 10/116,481.

The stimulator 10 comprises an electronics housing 11 attached to theinside of a stomach 100 and containing the stimulator electroniccircuitry 29 (FIG. 3). Leads 12, 13 are coupled to the electronicscircuitry 29 and extend from the housing 11 to terminate in stimulatingelectrodes 14, 15 respectively that are attached to the stomach wall.The housing 11 and the electrodes 14, 15 may be attached at a variety oflocations within or on the stomach, including but not limited to eitheron the greater curvature or the lesser curvature, or at the fundus orthe antrum. It is also contemplated that a plurality of electrode pairsmay be implanted at various locations in or on the stomach 100. Theelectrodes may be affixed by separate anchor or otherwise electricallycoupled to the stomach wall.

The housing 11 includes electronic circuitry 29. As shown in FIG. 3, theelectronic circuitry 29 of the stimulator 10 also includes a telemetrycircuit for communication with separate devices.

The electronic circuitry 29 receives sensing information; providesstimulating electronic pulses through the electrodes 14, 15 to thestomach wall; and telemetry communication with an external unit such asa reader, recorder or controller. The stimulator 10 may be incommunication with the electronic circuit 29 as described herein or witha separate controller (e.g. controller 70 in an external device 60 as inFIG. 4), which controls the stimulator 10.

Lead wire 12 includes separate impedance electrodes 16, 17 electricallycoupled to the electronic circuit 29 by way of separate electricalconnectors extending along lead wire 12. The impedance electrodes 16, 17are positioned to sense the impedance of contents of food in the stomachwhen they are interrogated. The impedance of the contents providesinformation on the food or liquid that has been ingested. For example,fat typically has higher impedance than carbohydrates. The impedanceelectrodes may be interrogated by the controller 40 (FIG. 3) orcontroller 70, after there is an indication that food has been ingested.Such indicators may include, for example, change in temperature, changein pH, change in stomach contractions, and change in pressure, asdescribed herein. The impedance sensors may also be interrogated on aperiodic basis. Thus, sensing and power expenditure can be limited tothe time at which the sensing is needed.

As illustrated in FIGS. 1A-1B, the housing 11 includes sensor 18 alocated on the housing and/or a sensor 18 b extending from the housing11. Alternatively or additionally, a sensor 18 c may be locatedseparately on the stomach wall and/or a sensor 19 may be otherwisepositioned adjacent or coupled to the subject. Sensors 18 a, 18 b, 18 care located within or attached to the stomach wall. Sensor 18 c may beattached to or otherwise coupled to or engaging the inside of thestomach wall, for example using a separate or integrally formedanchoring device, and may be introduced and attached to the stomach wallendoscopically or may be introduced and attached to the stomachlaparoscopically.

Sensor 19 is coupled to the patient. In this illustration, the sensor 19comprises a separately implanted device located subcutaneously within apatient's torso.

The sensors 18 a-c, 19 may each comprise one or more sensors thatprovide feedback on a condition of a patient or information relating tothe gastro-intestinal system of the patient. For example, the sensor maycomprise an accelerometer that detects patient gross movement and/orrespiratory movement from which patient state of wakefulness may bedetermined. The sensor 18 a-c, or 19 may be coupled to the electroniccircuitry 29 or to another control device by, leads to the electroniccircuitry 29 or other control device or by telemetric or othercommunication modes.

The sensors 18 a, 18 b, and 18 c are positioned to directly senseinformation concerning the stomach. The sensors 18 a-c may include, butare not limited to one or more of the following: temperature sensors,contraction sensors, pressure sensors, strain gauges, pH sensors,accelerometers, optical sensors. As noted above, the sensors 18 a-c areelectrically coupled to, or are otherwise in communication with theelectronic circuitry 29. (Alternatively they may be in communicationwith a separate or external controller, e.g., controller 70, thatcontrols the stimulation pulses in response to information sensed by oneor more of the sensors.)

The stimulator 10 comprises an anchor 123 and housing 11. The anchor 123comprises an elongate member 124 having and expandable distal end 125and a stimulating electrode 126 in the form of a ring of a corrosionresistant metal conductor. The stimulating electrode may be used insteadof or in addition to one of electrodes 14, 15. A strain gauge 121 isincluded on the elongate member 124 and is electrically coupled throughhousing 11 to electronic circuitry 29. The strain gauge 121 is locatedadjacent electrode 126 on the anchor 123, which acts to anchor theelectrode in the stomach wall. The strain gauge acts as a contractionsensor as described herein. Construction of and implanting techniquesfor such stimulator, for example, are described in U.S. Pat. No.6,535,764 incorporated herein by reference. The electronic circuitry 29provides sensing, stimulating electronic pulses through the electrodesto the stomach wall, and telemetry communication with an external unitsuch as a reader, recorder or controller.

FIG. 2 illustrates an alternative configuration of a stimulator inaccordance with the invention. The stimulator 20 comprises a housing 21implanted subcutaneously within a patient. The stimulator furthercomprises leads 22 a, 23 a extending from the housing 21 through theabdomen and to the stomach 100 where electrodes 22, 23 at the end of theleads 22 a, 23 a are implanted into the stomach muscle layer from theoutside of the stomach 100. A method of implanting the stimulatorhousing 21 and laparoscopically implanting the electrodes 22, 23 in thestomach 100 is generally known to those of ordinary skill in the art.

The housing 21 further comprises a sensor 24 a located on the housing 21and/or a sensor 24 b located elsewhere in the patient and coupled to theelectronic circuitry 29 (FIG. 3) in the housing 21 by lead 24 c. Thesensor 24 a or 24 b may, for example, include an accelerometer that isconfigured to sense motion of the patient. The stimulator also includessensors 25, 26, that are implanted on and in the stomach 100,respectively, with leads 25 a, 26 a extending from the sensors 25, 26 tothe housing 21. Sensor 26 is exposed to the inside of the stomach 100while sensor 25 is attached to the outside of the stomach. Leads 22 a,23 a and 24 c, 25 a, 26 a are electrically coupled to the electroniccircuitry 29 located in the housing 21. When the sensors 25, 26 areimplanted in the stomach, they may sense presence of material in thestomach, composition of such material and temperature, pH or pressurewithin the stomach, and/or patient motion corresponding to respirationor gross movement. Sensors positioned on the stomach may also sensevarious parameters that indicate the actions of the stomach, e.g.,movement, contractions. The sensors positioned on the stomach may alsoutilize various imaging techniques, e.g., ultrasound, and light, toidentify presence or composition of food or material in the stomach.

In use, once the stimulator (e.g., 10, or 20) is deployed electricalstimulation is provided through electronic circuitry 29. The electroniccircuitry 29 is capable of producing various types of programmablewaveforms that provide stimulation to the smooth muscle lining of theintestinal tract. It is well known to those of ordinary skill in theart, there are many different types of electrical stimulation programsand strategies which can be utilized for providing electricalstimulation parameters through the circuitry 29, the principal focusbeing providing electrically stimulating parameters for the stomach. Inone embodiment the focus of the electrical stimulation is to causegastric retention of food to produce a sensation of satiety. Anotherfocus of the electrical stimulation may be to interfere with the innateperistalsis of the stomach, which is intended herein to mean to movementof the stomach that typically also acts to break down food and/or movesmaterial towards the antrum or out of the stomach. Another focus is tocause a sensation of satiety by stimulating the stomach. Another focusis to control the secretions relating to the stomach or hunger bystimulating the stomach.

An embodiment of the electronic circuitry 29 is illustrated in FIG. 3.The electronic circuitry 29 of the stimulator is located in the housing11. The electronic circuitry 29 may be in a form of a standardized chipthat may be used with one or a variety of sensors, including but notlimited to those described herein. The electronic circuitry 29 orsimilar electronic circuitry may also be included with separatelyimplanted sensors or components of the system. Thus the variouscomponents may be configured to communicate with the other componentsthrough telemetry or similar signaling.

The circuitry 29 comprises, a microprocessor or controller 40 forcontrolling the operations of the electronic circuitry 29, an internalclock 41, and battery device 44 such as a pair of lithium iodinebatteries for powering the various components of the circuit 29. Assuch, the controller 40 and battery device 44 are coupled to each of themajor components of the circuit as would be apparent to one of ordinaryskill in the art. The battery 44 has its output supplied to a DC-to-Cconverter 44 a to provide a higher voltage, which is utilized forelectrical stimulation pulses. The DC-to-DC converter 144 a isconventional and provides an output voltage desired for stimulation. Theinternal clock 41 may also include a real time clock component thatcommunicates with the microprocessor 40. The real time clock componentmay be used to control stimulation, e.g. by stimulating or allowingstimulation only at a particular time of the day. The real time clockcomponent may also provide a date/time stamp for detected events thatare stored as information in a memory device. The memory may bepreserved by only saving information corresponding to an event ofinterest which is saved along with the time/date when the eventoccurred.

The controller 40 is coupled to stimulation driver 42, which is coupledto stimulating electrodes (e.g., 14, 15, 22, 23) that are used toprovide electrical stimulation in accordance with programmed parameters,including in response to sensing conditions relating to the patient orthe patient's intake of food as described herein.

The controller 40 is coupled to ROM 43, which contains the programinstructions for the controller 40 and any other permanently storedinformation that allows the microprocessor/controller 40 to operate. Thecontroller 40 addresses memory in ROM 43 through address bus 43 a andthe ROM 43 provides the stored program instruction to the controller 40via data bus 43 b. The controller 40 controls the telemetry coil 45,which communicates with an external control or programming device 60(FIG. 4), e.g., via a modulated RF signal. Processor 40 is coupled to abuffered oscillator 51 that provides an RF signal to be emitted from thetelemetry coil 45. The RF signal is preferably at about 100 kHz-5 Mhz sothat the signal is efficiently transmitted through tissue. Thecontroller 40 controls the oscillator 51 and provides data to bemodulated with the RF signal. For example, various sensed data such asmotion, transmitted or reflected light parameters, pressure, pH,temperature, local muscle contraction, strain, impedance, electricalactivity (EMG) etc., may be delivered via a modulated signal through thetelemetry coil 45. When the telemetry coil 45 is receiving an externaltelemetry signal, the buffered oscillator 51 is disabled. Telemetrysignals received on the telemetry coil 45 are detected in a detectorcircuit 51 a and communicated to controller 40. The detector circuit maybe selected based on the modulation used for the telemetry signals.

The circuit 29 may also be coupled through A/D converters (withamplifiers) 46 a, 46 b, 46 c, 46 d to one or more sensors 18 a-c and 19,or, 25, 26, 24 a, 24, 121 respectively. The A/D converters convert arepresentative analog electrical signal from the sensors into a digitalsignal communicated to the controller 40. Suitable types of thesesensors may include but are not limited to the types of sensor describedherein. Such sensors at various locations are coupled to the electroniccircuit by way of lead wires or through alternative means ofcommunication such as telemetry, wireless communication or indirectlythrough a separate controller e.g., controller 70.

Controller 40 is coupled to RAM 50 via an address bus 50 a foraddressing a location in RAM 50 and a bi-directional data bus 50 b fordelivering information to and from RAM memory 50. The RAM memory 50includes event memory 48 that temporarily stores data recorded bysensors 18 a-c, 19, 24 a, 24, 25, 26, or electrodes 14, 15; 16,17; or23; 23. RAM memory 50 also includes a programmable memory 49 which maybe programmed, for example, by an external programmer 60. The datastored in the programmable memory may include specifications for theelectrical stimulation operating modes (e.g., waveform, type ofstimulations: for pacing, inducing, interfering with or reversingcontraction, for interfering with innate activity, for controllingbiochemistry or secretions relating to the stomach, or other types ofstimulation) and various procedures or responsive parameters (e.g., forturning on or off various sensing or stimulation functions, parametermodification, protocols or procedures for recognizing various conditionsof the patient of the patient's gastrointestinal tract and protocols orprocedures for responding to such recognition). These data andprocedure/protocol elements, including responsive elements that respondto sensed data, may also be located in whole or in part in othercontroller devices that may be located independently from electroniccircuitry 29. The programming may be done in response to sensedinformation or, it may be done automatically by an external controlleror as desired by a treating physician, etc. Sensed data acquired fromthe sensors or electrodes, provided to the controller 40 may be storedin event memory 48 in the RAM 50. The data stored in the event memory 48may be sent intermittently as data bursts via the telemetry coil 45, asopposed to continuously, in order to save battery power. The clock mayalso mark or date/time stamp the data stored in event memory. Theprocessor also may select events based on predetermined thresholds orcharacteristics that are to be stored as a significant event, whileother events are filtered out and not stored.

The electrodes 14, 15 or 22, 23 are coupled through A/D converters 46 eand 46 f to the microprocessor 40. A/D converter 46 e converts theelectrical EMG signal sensed by the electrodes 14, 15 or 22, 23 into adigital signal representative of the EMG electrical activity, which isdelivered to the microprocessor/controller 40 and stored in the eventmemory 48 in the RAM 50. Also, the A/D converter 46 f converts theelectrical signal sensed by the electrodes 14, 15 or 22, 23 and providedthrough the impedance circuit 53 described below, into a digital signalrepresentative of tissue impedance, which is delivered to themicroprocessor and stored in the event memory 48 in the RAM 50.

The electrode 14, 15 or 22, 23 outputs are used to provide electricalstimulation delivered through the stimulation driver 42 to electrodes.The stimulation modes and parameters can either be set using theexternal programmer 60, or they may be set in response to sensoryfeedback. The same electrode outputs may be used to sense impedance ofthe stomach tissue or of the contents of the stomach depending upon thelocation of the electrodes. Impedance circuit 53 is used to senseimpedance and EMG or other electrical activity information is providedto the processor 40 through A/D converter 46 e. The electrodes 14, 15 or22, 23 are coupled through coupling capacitors 55 a and 55 brespectively, to output of electrical stimulation driver 42 and input ofA/D converters 46 e, 46 f.

The impedance circuit 53 comprises a constant current source oscillator54 that oscillates at a frequency of 50-100 kHz, and A/D converter 46 fwith an output coupled to the controller 40. The oscillator 54 providesa constant current source through electrodes 14, 15 or 22, 23 resultingin a voltage across the electrodes 14, 15 or 22, 23 that isrepresentative of impedance, in view of the constant current. Thevoltage is provided through and is converted by A/D converter 46 f to adigital signal representative of impedance. A/D converter 46 f has abandwidth that includes the 50 kHz frequency signal while filtering outthe electrical stimulation signal that is delivered to the electrodes14, 15 or 22, 23 through electrical stimulation driver 42, and the EMGsignal that is sensed by the electrodes 14, 15 or 22, 23. Both of theoutputs are filtered out by A/D converter 46 f. A/D converter 46 e has abandwidth that filters out the 50-100 kHz signal. Further, when astimulation signal is being delivered, the controller 40 does notreceive signals from A/D converters 46 e and 46 f. Thus the EMG andimpedance sensing functions and the stimulation deliver functions may beseparated through the electronic circuitry 29, though using the sameelectrodes.

An additional circuit 58 may be provided in the electronic circuitry 29comprised of similar components configured like impedance circuit 53.The circuit 58 delivers an interrogating electrical pulse to theelectrodes 16, 17 and senses impedance of material between theelectrodes. The electrodes 16, 17 are positioned to be in electricalcontact with contents of materials that may be in the stomach. Asillustrated in FIGS. 1A-1B, the electrodes 16, 17 are located onseparate leads along lead wires connecting the electrodes 14, 15 to thestimulator housing 11. An A/D converter coupled to the controller 40converts the sensed information into a representative signalcommunicated to the controller 40.

Additional stimulating sensing electrodes and corresponding signalprocessing circuits may also be provided.

FIG. 4 illustrates the electronic circuitry 63 for external programmer60. The electronic circuitry 63 comprises: a microprocessor orcontroller 70 for controlling the operations of the electroniccircuitry, an internal clock 71, and a power source 74 such as batterydevice for powering the various components of the circuit 63. As such,the controller 70 and battery device 74 are coupled to each of the majorcomponents of the circuit as would be apparent to one of ordinary skillin the art. The controller 70 is coupled to a speaker 67 that providesaudible alerts and a display 66 such as a CRT to display data such asrecorded data, sensed parameters, treatment parameters and status ofdevice (e.g. position or battery charge status). The controller 70 iscoupled through a buffer 64 to external input device 65 that is used toprovide program parameter input, e.g. from a user, for a user to requestdata displayed in a desired format through display 66 or speaker 67, orto turn device on and off. The external programmer 60 is also providedwith an external data port 68 to interface with a computer and provide ameans for bi-directional communication of data or commands. The computermay provide programming or data to the controller/microprocessor 70. Auser may also interface with the computer to provide treatment protocolsor changes in protocols, etc. Also, a user may control the turning onand off of the stimulation program.

The controller 70 is coupled to ROM 73, which contains the programinstructions for the controller 70 and any other permanently storedinformation that allows the microprocessor/controller to operate. Thecontroller 70 addresses memory in ROM 73 through address bus 73 a andthe ROM 73 provides the stored program instruction to the controller 70via data bus 73 b. The controller 70 controls the telemetry coil 75,which communicates with stimulator electronics 29 (FIG. 3) through itstelemetry coil 45. Controller 70 is coupled to an oscillator 72 thatprovides an RF signal, preferably having a characteristic frequency of500 kHz or higher, to be emitted from the telemetry coil 75. Thecontroller 70 controls the oscillator 72 and provides data to bemodulated with the RF signal, for example, programming information,stimulation parameters, etc. The telemetry coil 75 also receivesinformation transmitted via RF signal from telemetry coil 45 on thestimulator 10 such as various sensed data, e.g., temperature, pressure,pH, impedance of the stomach or of its contents, optical characteristicsof stomach contents, motion data, electrical activity (EMG), etc. Thereceived RF signal is passed through A/D converter 76 and is transmittedto the controller 70. The data is delivered to the event memory 78 inRAM 77 by way of data bus 77 b for temporary storage. The data may beretrieved from RAM 77 by addressing the storage location via the addressbus 77 a.

Event memory 78 temporarily stores data sensed by sensors 18 a-c, 19, 24a, 24, 25, 26, 121 or electrodes 14, 15, 16, 17, 22, 23; recordedthrough controller 40; and delivered via telemetry to the externalprogrammer 60. The data may then be downloaded onto a computer using theexternal data port 68. The RAM 77 also includes a programmable memory 79which may be programmed, for example, to specify operating modes such aswaveform, frequency, pulse width, amplitude, repetition rate, etc. whichprogramming is then telemetrically communicated to the stimulationdevice 10, 20. The modes and parameters can either be set using anexternal programmer 60 and/or set in response to sensory feedbackaccording to programs.

The stimulator 10 or 20 may be programmed to deliver electricalstimulation in response to sensed parameters. The sensors 18 a-c, 19, 24a 24, 25, 26, 121 or electrodes 14, 15, 16, 17, 22, 23, depending upontheir specific location, may comprise (but are not limited to): atemperature sensor that may sense a change in temperature or a rate ofchange in temperature that indicates ingestion of food or liquid; a pHsensor that may be used to determine when food has been ingested; anoptical emitter/sensor that may be used to determine the presence and/orcomposition of food; a pressure sensors that may be used to sensemotility patterns, e.g. presence, strength or frequency of contractions;a contractions sensor that may provide information on stomachcontractions an local responses to stimulation; an impedance sensor thatmay provide information on the content of the stomach and/or animpedance sensor that may determine when a characteristic EMG patternexists to determine wakefulness of a subject; a motion sensor thatdetermines an activity level or wakefulness of a subject; a biochemicalsensor that provide information on biochemical compositions relating tothe stomach such as secretions.

The responsive devices may comprise at least one sensor and at least oneresponsive element. From sensed information, the responsive elementdetermines the existence of a condition, e.g., presence of food;ingestion of food; type of food ingested; activity level of a subject;wakefulness of a subject; time of a daily cycle or schedule;contractions of the stomach, etc.

The responsive element may combine a number of sensed parameters todetermine the existence of a condition or circumstance or a probabilityof the existence of a condition or circumstance. The responsive elementmay thereupon determine a course of treatment, including protocols,stimulation parameters and whether or not to stimulate. In one variationresponsive element may respond by stimulating to interfere with thestomach contractions; to slow, stop or reverse the innate peristalticcontractions that tend to move food through the stomach.

For example, the combined determination of temperature changesindicating likelihood of food ingestion, and an accelerometer indicatingthat a subject is not sleeping or is not highly active may trigger aresponsive element to stimulate the stomach to retain food for apredetermined period of time. The accelerometer can determine a lowlevel of activity indicating likelihood of a sleep state, but may beoverridden by a temperature sensor sensing that food has been ingestedand thus requiring stimulation. PH may be used in a similar manner astemperature to indicate a likelihood of food ingestion. A timer may alsoconfirm the likelihood that food is being eaten given the time of day,or may refrain from stimulating in spite of food being ingested if it isa certain time of day, e.g., when the stomach is naturally cleaning outthe stomach as it typically does during the night.

The responsive element may receive input from one or more sensors and,in response, the responsive element may interrogate another sensor forinformation to determine a course of action. This may be used to savebattery or power consumption. This may also be used to confirm theexistence of a condition or circumstance using more than one sensor. Forexample, one or more sensors may provide information that food has beeningested. Upon making this determination, another sensor may betriggered to determine what type of food has been ingested. For example,an impedance sensor may determine characteristics of the content of thestomach by measuring the impedance of the contents of the stomach. Anoptical emitter/sensor may sense the light reflectance/transmissioncharacteristics of contents of the stomach. This information may berecorded in a memory device and downloaded. Also the information mayelicit a simulation response controlled by the responsive element when acertain type of food is detected. In addition foods may be provided aspart of an eating regimen that have markers for different types of food.Gastric retention of some foods may be created while permitting movementof others out of the stomach.

FIG. 5 illustrates an exemplary processed temperature signal sensed by atemperature sensor over a period of time. The temperature sensor ispositioned in the stomach to sense temperature or temperature changesthat may occur due to a subject ingesting material such as food orliquid. Sensors 18 a, 18 b, 18 c, or 26 may be suitable as temperaturesensors that are positioned within the stomach.

As illustrated in the exemplary sensed signal in FIG. 5, temperature ison the y-axis while time is on the x-axis. From time t₀ to t₁, thetemperature sensed is relatively constant, at core body temperature ofabout 37 degrees Celsius. Between time t₁ to t₂, warm food is ingestedby a patient and the sensor senses a characteristic temperature overtime as indicated by the temperature signal from time t₁ to t₂. Fromtime t₂ to t₃, temperature has again returned to normal. From time t₃ tot₄, temperature changes much more gradually and to a lesser degree thanfrom time t₁ to t₂. This temperature fluctuation does not meet atemperature threshold T_(h) (high) or T₁ (low). The absolute change intemperature and the rate of change in temperature are also less than theabsolute or rate of change in temperature from time t₁ to t₂. From timet₄ to t₅, the temperature is again approximately normal at 37 degreesCelsius. From time t₅ to t₆ cold substance is ingested by a patient andthe sensor senses a characteristic temperature over time as indicated bythe temperature signal from time t₅ to t₆.

The signal is processed either by controller 40 or is telemetricallytransmitted by electronic circuit 29 to external programmer 60. Thecontroller 40 or controller 70 may process the signal in a variety ofways to determine whether the characteristic signal in a period of timeindicates that food or other material has been ingested. For example,from the sensed temperature signal, a change in temperature over timefor the signal or absolute change in temperature may be derived ordetermined. If the change is substantially fast and of a significantdegree, it determines that food or a substance has been ingested. Thus,using one or more temperature parameters, e.g., actual temperaturesensed, change in temperature or rate of temperature change, adetermination may be made that a subject has ingested material.Additionally, or alternatively other characteristics of a sensedtemperature signal may be observed to conclude that the signal ischaracteristic of ingestion of material, ingestion of a certain type ofmaterial (e.g., liquid or food), or of a threshold amount of material.For example, the sensed signal may be compared to a characteristicsignal a comparison from which, a requisite amount of or degree ofcorrelation with a characteristic material ingesting signal may causethe processor to conclude that a requisite amount of food has beeningested. A responsive element then responds either by stimulating ornot stimulating the stomach, by increasing, decreasing stimulation or byaltering stimulation parameters.

FIGS. 6A and 6B illustrate schematic exemplary accelerometer signalsfrom one axis of a multi axis accelerometer The y-axis corresponds todetected motion while the x-axis represents time. Referring to FIG. 6A,between time t_(a0) to t_(a1), activity is minimal showingcharacteristic movement corresponding to sleeping and respiration duringsleeping. During this period, stimulation is turned off. From timet_(a1) to t_(a2), a burst in activity is sensed and then again frombetween t_(a2) and t_(a3). From time t_(a3) to t_(a4), the signalreturns to the characteristic sleep and sleep respiration pattern. Inthis exemplary signal, the bursts in activity correspond to grossmovement that may occur during sleep. This may be determined among otherways, by observing the movement returning to a typical sleeping patterna short time after the gross movement occurs. The controller 40 of theelectronic circuitry 29 or (or other controller or processor to whichsensed data is supplied) is programmed to recognize the sleepingrespiration movement and gross movements that correspond to movementduring sleep. The program may compare a number of signal parameters andfind a certain degree of correlation from which a determination of acondition is made. Such conditions may include for example, sleeping,resting but not sleeping, gross movement during sleep, or an exertionlevel. For example the sleep respiration pattern may include arespiration rate or pattern corresponding to sleep. If the grossmovements are relatively short and the signal returns to the sleeprespiration pattern, then the controller may be programmed to recognizethe gross movement as “gross movement during sleep”. If the movement isfairly rapid and at relatively higher amplitude, the controller may beprogrammed to determine that a higher exertion level exists.

Referring to FIG. 6B, between the time t_(b0) to t_(b1), activity isminimal and characteristic of sleeping. During this period, stimulationis turned off. From time t_(b1) to t_(b2) a burst in activity is sensedand again from time t_(b2) to t_(b3) gross movement is sensed. Themovement from time t_(b1) to t_(b2), and from time t_(b2) to t_(b3) ischaracteristic of movement during wakefulness. The signal does notreturn to a characteristic sleep movement pattern. The controller isprogrammed to recognize this gross movement or continuation of suchgross movement for a period of time as activity during a waking state.The controller may also compare the gross movement and detectedrespiration from movement of the chest to confirm the determination ofthe state of wakefulness of a subject. The movement from time t_(b2) tot_(b3) is more rapid and of greater magnitude indicating a greater levelof exertion. The controller or processor processing the signal may, forexample, recognize the activity level as a high level of exertion if theactivity continues for a significant amount of time. The controller mayaccordingly then control the signal to turn the signal off during theperiod of high exertion. The controller may be programmed to recognize anumber of parameters of the accelerometer curve including rate of changein motion, amplitude of motion signal and other types of motion havingcharacteristic signals.

In addition to characteristics such as the ingestion of food beingfactored into a programmed device response, innate characteristics ofthe stomach may be sensed and used to make decisions relating to or tocontrol or modify stimulation. For example, innate stomach contractionsmay be observed periodically. Without food intake, if the contractionsincrease, it may be determined that the subject is getting hungry orwill be getting hungry. The responsive device may be programmed torespond to such an indicative contraction pattern by controlling thestomach contractions, for example, by interfering with the contractions.Alternatively or additionally, a biochemical sensor may be used toidentify the presence, absence or quantity/concentration of abiochemical substance such as a hormone related to hunger (e.g.ghrelin), or another stomach secretion such as an enzyme or acidiccomposition. The responsive device may respond to the information bystimulating. The information may also be stored and communicated to anexternal device or downloaded at a later time to enable the subject tootherwise respond or to observe subject patterns over time.

Referring to FIG. 7 an optical sensor 80 is illustrated extending fromthe housing 11 of the stimulator 10 within the stomach. The opticalsensor 80 includes a distal end 81 configured to illuminate and sensethe optical characteristics of food or other material within thestomach. The optical sensor 80 uses spectroscopy by detecting lightabsorption, reflectance or excitation characteristics that correspond tovarious compositions of materials in the stomach.

According to one embodiment of the invention, the sensor light sourceemits and detects light or absence of light of certain wavelengths.According to this embodiment, the sensor 80 includes at least one lightsource, e.g. an LED or optical fiber source that emits either a whitelight or light of one or more particular wavelengths. The light source84 is controlled by the controller, which directs a brief pulse of lightinto the intestinal tract or at the contents of the stomach. The sensor80 further includes at least one sensor for sensing reflected ortransmitted light. The reflected or transmitted light indicatesparticular reflectance or absorption of certain wavelengths of lightcharacteristic of certain materials or substances. The excitationcharacteristics of the object and/or the absorption of a particularwavelength (non-reflectance) of light to which a photo diode issensitive is determined when the photo diode senses or does not sense asufficient amount of light corresponding to a particular wavelength. Thesensor 80 is coupled to the processor 40 through processing circuit 59(FIG. 3). The processing circuit 59 energizes the optical fibers orLED's upon receiving instructions from the processor 40. The processorcircuit 59 also receives signals from the light sensing portions of thesensor corresponding to sensing reflected or transmitted light andconverts the signals into a digital signal that is communicated to theprocessor 40. The processor 40 or processor 70 receiving related datafrom the electronic circuitry 29, determines whether or not certainmaterials or compositions are present based on the sensed reflected ortransmitted light.

In response to sensing presence of food of a particular composition, thedevice may do one of several things. For example, the device maystimulate the stomach to retain the food based on the detected foodcomposition. The device may stimulate the stomach to provide a sensationof satiety or a slightly uncomfortable sensation if a substance isdetected that is not part of a pre-approved eating regimen, e.g., a fat,carbohydrate or type of carbohydrate (e.g., simple or complex).

In one embodiment, pre-approved food are produced with a marker a, e.g.,a fluorescing marker. If an unapproved food is eaten, the deviceresponds by stimulating the stomach to create an unpleasant sensation.Thus training the individual to dislike the unapproved foods.

The optical sensor 80 may be interrogated by the controller 40delivering a control signal to the processing circuit 59, whichinterrogates the sensor 80 to sense the contents of the stomach. Inorder to save device power, this control signal may be delivered only ifingestion of food is sensed, e.g. with a temperature sensor as describedabove. The sensor 80 in one embodiment is interrogated immediately aftersensing ingestion of material so that the composition of the materialmay be sensed prior to initial breakdown of the material by digestiveenzymes. The device may also record a log of sensed information fordietary tracking purposes that can be downloaded after a period of time.

Referring to FIG. 8, one variation 81 a of a distal end 81 of theoptical sensor 80 is illustrated. The variation 81 a of the distal endcomprises light emitter detectors 82 _(1-n), each of theemitter/detectors 82 _(1-n) comprising light fibers and light sensors(e.g. photodiodes) emitting and detecting particular correspondingwavelengths of light λ_(1-n) (where n is a positive integer). Theemitter/detectors 82 _(1-n) may alternatively comprise LED's and lightsensors. The emitter/detectors 82 _(1-n) illuminate the contents of thestomach and then detect the resulting reflectance of light or theexcitation characteristics of the contents of the stomach for theparticular wavelengths of light λ_(1-n). The sensed light is convertedto a representative signal by processing circuit 59, which processessensing light information in a manner that would be apparent to one ofordinary skill in the art.

Referring to FIG. 9 a variation 81 b of the distal end 81 of the opticalsensor 80 is illustrated. The variation 81 b of the distal end 81comprises a concave portion 86 forming an opening 87 for temporarilyreceiving a portion of the contents of the stomach 100. The opening 87includes a proximal end 84 a and a distal end 85 a. This variation 81 bof the distal end 81 comprises photo diode detectors 85 located on theconcave portion 86 at the distal end 85 a of the opening, and LED lightsource 84 on the concave portion 86 at the proximal end 84 a of theopening 87. In this embodiment a white light source is used. The lightsource 84 and the photo diode detectors 85 are arranged with respect toeach other such that light emitted from the light source 84 is receivedand sensed by the photo diode detectors 85. The photo diode detectors 85may comprise an array of detectors or filters, each sensing a particularwavelength or range of wavelengths of light. Alternatively, a pluralityof LED emitters of predetermined wavelengths (e.g. with filters) may beused to illuminate the stomach. Absorption of particular wavelengths maybe used to determine presence or absence of various compounds.

The array of detectors is coupled to the processing circuit 59, which iscoupled to the processor 40. The processing circuit 59 is configured toselect the sensors or filters that correspond to wavelength(s) to bedetected, e.g., based on a selected diagnostic mode. The processor 40may select a particular substance or food, etc. for which to sense. Thismay be preprogrammed into the processor 40 or may be modified during thecourse of treatment or diagnosis with the stimulator system. Theprocessor 40 instructs the processing circuit 59 to cause emission oflight and then sense light transmitted through material located withinthe opening 87.

In use, food or other material in the stomach is accumulated in theopening 87 through which light is transmitted. The photo diode sensors86 sense light that is transmitted through the food or material in theopening 87. The photo diode detectors 85 are selected to detectdifferent wavelengths of light. The food has a characteristic lightabsorption that can be used to identify the composition of the food. Thelight characteristics of the stomach tissue and corresponding lightabsorption or reflectance signal can be filtered out of the signalleaving a signal corresponding to the contents of the stomach. Theresulting sensed light signal is processed by the processing circuit 59,which transmits a representative digital signal to the processor 40corresponding to the transmitted light sensed by the photo diodedetectors 85.

As described above, the electronics circuit 29 is configured to receivesensed signal(s) indicative of optical parameter(s) such as one in whichpresence of certain foods is indicated. The sensed signal iscommunicated to the processor 40, which communicates a signalrepresentative of the sensed information via the telemetry coil 45 to anexternal controller/processor 70. The information may, for example, bein the form of a composite signal combining sensed light information ofeach of the sensors, or may be temporally spaced signals for each of thesensors.

In another embodiment the device senses contraction by sensing pressure.The pressure within the stomach generally increases with an increasedrate of contraction. For example, a pressure of about 250-300 mm Mercuryindicates a level of contractions corresponding to a higher level ofstomach activity that would be beneficial to suppress in order tocontrol hunger. If the patient is in a state in which appetite is to besuppressed, then upon sensing contractions, the stomach is stimulated toreduce the contraction and thereby reduce hunger pangs. The pressuresensor may be located in the stomach such as sensor 18 a, 18 b, or 26.The pressure sensor may be located within the housing where the housingis constructed having a sufficiently thin wall to permit pressurechanges to be sensed within the housing.

In another embodiment, a contractions sensor is positioned in or on thestomach wall such as sensors 18 a, 18 b, 18 c, 25 or 26, 121 and sensesstomach contractions. In response to sensing contractions, a responsiveelement may cause the stomach to be stimulated to manipulate the stomachcontractions, e.g., by reducing or reversing the contractions.

During sleep, the stomach goes through a cleaning process. This processcan be observed by pressure changes and emg signals characteristic of asleep cycle. Accordingly, stomach emg can be monitored and stimulationcan be prevented when such signal is present. Other indicators of sleepsuch as from an accelerometer can be used to confirm the sleeping stateof the subject.

A real time clock may also be used to determine the times to stimulateor to not stimulate, e.g., on a daily schedule. For example a real timeclock may in combination with a sleep sensor determine when to turn offstimulation, e.g. when the subject is supposed to be sleeping and whenthe parameters sensed indicate that the patient in fact is sleeping. Thestimulation may be turned off a certain meal times to allow the subjectto eat without interference of the peristaltic signals and to permitnormal digestion of food.

The invention has been described with reference to preferred embodimentsand in particular to a gastric stimulator, the present inventioncontemplates that a number of combination of sensors may be used todetermine the state of a patient or the gastrointestinal tract of thepatient and to determine, if, when and how to stimulate the stomach inresponse. A number of different signal and information processingtechniques may be used to arrive at a stimulation protocol ormodification thereof. A number of different communication schemes may beused between, the sensor processors and stimulation electrodes. Also themeans for powering the implanted portions of the device may also vary inaccordance with various techniques and devices.

The responsive element or responsive device may include one or morecomponents that are located together or separately. For example a signalprocessing component may be located in an implanted device and acontroller for determining the existence of a particular condition maybe located in a separate component directly or indirectly incommunication with the signal processing component.

Other instruments and devices may be used to determine stimulationparameters locally at a stimulation site, in response to stimulation ata particular stimulation site. Referring to FIGS. 11A and 11B, anendoscopic instrument 480 is used to map electrical activity in thestomach wall and to identify and characterize the response of thestomach wall to various electrical stimulation parameters. Theinstrument 480 comprises an elongate flexible member 481 generallyformed of a coil 482 with a lumen 483 extending therethrough. An endeffector 484 is located at the distal end of the instrument 480. The endeffector 484 comprises electrode members 486, 487 coupled together by ahinge 485. The electrode members 486, 487 include electrodes 488, 489located at the ends of the members 486, 487. The electrodes 488, 489 arecoupled through conductors 490, 491 extending through electrode members486, 487 to wires 492, 493 which extend through the lumen 483 in theinstrument 480 to a proximally located handle 499. The wires 492, 493are coupled to an external stimulator/recorder unit 498, which suppliesstimulation energy to electrodes 488, 489 through wires 492, 493 andrecords electrical activity sensed by the electrodes through the wires492, 493. A mechanical wire 494 is coupled to a hinge actuating device495 and extends through the lumen 483 to handle 499. The electrodemembers 486, 487 are initially in a closed position. When the wire 494is moved distally using handle 499, the hinge actuating device 495rotates the electrode members 486, 487 about hinge 485 to spread theelectrode members 486, 487 and electrodes 488, 489 apart from eachother. In this position (FIG. 11A-11B); the electrodes may be placed onthe stomach wall at a desired site to measure and record electricalactivity, electrical parameters, or to provide electrical stimulationpulses to the stomach wall. Upon providing stimulation pulses to thestomach wall, the response of the stomach (e.g., the presence, absenceor degree of contraction) may be observed, either visually or through asensor (not shown) located on the end effector 484 that senses musclecontractions, such as, for example, a strain gauge. The ideal locationfor attaching a stimulation device may be determined by sensingelectrical activity, electrical parameters or by observing a locationwhere stimulation results in a desired response. Also the idealstimulation parameters or program may also be determined with the deviceby observing the response of a site to various stimulation parametersdelivered by the end effector 484.

FIG. 10 is a flow chart illustrating operation of a stimulator accordingto one aspect of the invention. As is readily understood by one ofordinary skill in the art, the operation of the stimulator as set forthin FIG. 10 may be accomplished with readily recognizable structuralelements, including, for example, a CPU or processor in conjunction witha program saved in a memory device. The stimulator first stimulatedtissue 301 at a stimulation site. A local sensor in close proximity tothe stimulation site senses a local contraction response at thestimulation site 302. If the contraction has not reached a suitablecontraction threshold 303, e.g. preset or pre-programmed into thestimulator, the stimulation 301 and sensing 302 steps are repeated. Ifthe contraction has reached a threshold 303, then the stimulation is setat the threshold or a preset amount above the threshold. 305.Stimulation then follows a protocol such as a protocol described hereinwhere stimulation is provided under a certain set of circumstances andfor a certain purpose, e.g., to control appetite 306. At a predeterminedtime, upon occurrence of a predetermined event, or at the request of aprogrammer, (e.g. through the external controller by a subject orprovider), a check is made for flags indicating stimulation may need tobe readjusted. 307. Such flags may include a preset passage of time, aoccurrence of preprogrammed set of circumstances (e.g. based onalgorithms defining the stimulation protocol or identifyingcircumstances that may indicate stimulation is not effectively beingdelivered). If the flags indicate stimulation reassessment is notrequired 308, the stimulator returns to step 306 wherein the stimulationprotocol is again followed. If stimulation reassessment is required 308then the stimulation step 301, the sensing step 302 and stimulationparameter setting step 305 are repeated as described above. Thestimulator in accordance with the invention may include a plurality ofelectrodes and sensors that are independently tested and set forindependently determined parameters.

While the invention has been described with reference to preferredembodiment, it will be understood that variations and modifications maybe made within the scope of the following claims. Such modifications mayinclude substituting elements or components that perform substantiallythe same function in substantially the same way to achieve substantiallythe same result that the invention can be practiced with modificationwithin the scope of the following claims.

1. A method for treating a subject having a stomach with a stomach wallsurrounding a cavity of the stomach, the method comprising: implantingelectronic circuitry within the subject; supporting a temperature sensorwithin the cavity of the stomach so as to measure a temperature withinthe cavity; electrically coupling a stimulating electrode to the wall ofstomach; operatively coupling the circuitry to the temperature sensor;operatively coupling the circuitry to the stimulating electrode; sensingthe temperature within the cavity of the stomach with the temperaturesensor; determining, using the circuitry and in response to the sensedtemperature, a rate of change of the temperature within the cavity ofthe stomach; identifying, using the circuitry and in response to therate of change of the temperature within the cavity of the stomach, aningestion of material by the subject; and stimulating the stomach byenergizing the electrode using the circuitry in response to theidentified ingestion of material by the subject.
 2. The method of claim1 further comprising: sensing another parameter from the subject; anddetermining, with the circuitry and in response to the other sensedparameter; a condition of the subject, wherein the stimulation of thestomach is performed in response to the determination of the conditionof the subject.
 3. The method of claim 2, wherein determining thecondition of the subject comprises determining whether the subject issleeping or awake, and wherein stimulation of the stomach is inhibitedin response to a determination that the subject is sleeping.
 4. Themethod of claim 2, wherein determining the condition of the subjectcomprises determining whether the subject is sleeping or awake, andwherein the stimulation of the stomach is performed in response to adetermination that the subject is sleeping.
 5. The method of claim 2wherein the other parameter sensed corresponds to muscle contractions ofthe stomach.
 6. The method of claim 5 wherein the other sensor comprisesa pressure sensor.
 7. The method of claim 2, wherein the temperaturesensed from within the cavity of the stomach varies in response to atemperature of the material ingested by the subject.
 8. The method ofclaim 2, wherein supporting the temperature sensor comprises affixing ananchor to the stomach wall with the temperature sensor extending awayfrom the stomach wall and into the interior of the stomach.
 9. Themethod of claim 8, wherein affixing the anchor to the stomach wall isperformed using an elongate member extending through the stomach wall byengaging an inner surface of the stomach wall with a first surfacecoupled to the elongate member, and by engaging an outer surface of thestomach wall with a second surfaces coupled to the elongate member sothat the stomach wall is disposed between the first surface and thesecond surface, and wherein electrically coupling the electrode to thestomach wall is performed by inserting the elongate member through thestomach wall, the electrode being disposed on the elongate member.